1. Field of the Invention
The present invention relates to a closed compressor accommodating lubricating oil which is incompatible with a refrigerant.
2. Description of Related Art
FIG. 8 depicts a conventional compressor comprising a compression mechanism 1, a rotary shaft 2 connected to the compression mechanism 1, an electric motor 3 for rotating the rotary shaft 2 to drive the compression mechanism 1, and a closed vessel 4 in which the compression mechanism 1, the rotary shaft 2 and the electric motor 3 are accommodated. The closed vessel 4 also accommodates lubricating oil 5 stored at a bottom portion thereof. The rotary shaft 2 has an oil supply pipe 6 secured to a lower end thereof to introduce the lubricating oil 5 to the compression mechanism 1.
In use, when the electric motor 3 rotates the rotary shaft 2 together with the oil supply pipe 6, the oil supply pipe 6 draws up the lubricating oil 5 stored at the bottom portion of the closed vessel 4 so that the compression mechanism 1 is lubricated. The lubricating oil 5 takes heat from the compression mechanism 1 and the electric motor 3 and then heat-exchanges with the closed vessel 4, which in turn radiates heat to the outside air.
In the above-described construction, however, if the lubricating oil 5 is incompatible with a refrigerant, a liquid refrigerant is accumulated in the bottom portion of the closed vessel 4. In general, the lubricating oil 5 and the liquid refrigerant 7 so accumulated in the bottom portion are separated into two phases. In this case, it is likely that the liquid refrigerant 7 having a specific gravity greater than the lubricating oil 5 and, thus, sitting below the lubricating oil 5 would be introduced into the compression mechanism 1 through the oil supply pipe 6. Consequently, the lubricating action to the compression mechanism 1 is lowered, the wear of the compression mechanism 1 is accelerated, and a temperature rise of the electric motor 3 is brought about. As a result, the reliability of the closed compressor is lowered. This phenomenon becomes conspicuous, particularly when the liquid refrigerant is returned back into the compressor during operation.